Abstract
Using congruences, a Hoehnke radical can be defined for graphs in the same way as for universal algebras. This leads in a natural way to the connectednesses and disconnectednesses (= radical and semisimple classes) of graphs. It thus makes sense to talk about ideal-hereditary Hoehnke radicals for graphs (= hereditary torsion theories). All such radicals for the category of undirected graphs which allow loops are explicitly determined. Moreover, in contrast to what is the case for the well-known algebraic categories, it is shown here that such radicals for graphs need not be Kurosh–Amitsur radicals.
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Veldsman, S. Hereditary Torsion Theories for Graphs. Acta Math. Hungar. 163, 363–378 (2021). https://doi.org/10.1007/s10474-021-01134-w
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DOI: https://doi.org/10.1007/s10474-021-01134-w
Key words and phrases
- graph congruence
- Hoehnke radical
- connectedness and disconnectedness of graphs
- Kurosh–Amitsur radical
- ideal-hereditary radical
- torsion theory